Like many authors his age, Bell is better at asking questions than answering them. It reminds me of something I learned in the Navy: never bring up a problem without also bringing up a solution. Bell brings up many problems, and few solutions.
This book also contains his trampoline analogy, in which doctrines are compared to trampoline springs. Yes, a trampoline will work just fine with a few springs missing, just as you can be a Christian without holding to all of some doctrines. Bell's analogy fails at two points, though.
First, it ignores the fact that if you keep removing springs, you'll eventually find yourself not bouncing on a trampoline, but standing on the ground. Second, doctrines often build on each other , and taking one out may take out several otherwise solid ones with it.
Bell has embraced postmodernity, with its denial of absolute truth, closely, and I can't recommend his books.